We have a Salesforce Site with a single Visualforce page which displays a record from a custom object. The associated custom controller has an action which updates the record. The controller class is defined as Public Class MyClass.

So, since the Spring 21 release, the Guest User profile no longer has Edit permissions on the Custom object. No problem I thought, the controller is just defaulting to 'with sharing' and I need to explicitly make it 'without sharing' so that it runs in System Mode and has full access to all fields and permissions on the custom object. So my class definition is now Public without sharing Class MyClass.

But this didn't make any difference and I'm still getting the error -
System.VisualforceException: Update access denied for MyCustomObject__c, controller action methods may not execute

I'm thinking that this is not going to be possible to fix, without using a licence or community setup. I would be grateful for any advice.

Hello,
I set up the JIT SSO configuration for communities and passing these attributes :

Contact.Email

Contact.LastName

User.Email

User.FederationIdentifier

User.LastName

User.ProfileId

User.Username

eduPersonPrincipalName

email

givenName

surname

uid External users can log in and it also creates a new community user but for existing internal users. I am getting errors :  https://abc.my.salesforce.com/_nc_external/identity/saml/SamlError?ErrorCode=5&ErrorDescription=Unable+to+create+user&ErrorDetails=Changing+User+Type+from+Standard+to+MSSC+Community+Portal+Login+User+is+not+allowed.+Select+a+different+profile.